URMS speed of methane gas CH4 at 11.1 degrees Celsius?

urms = square root (3RT/M) where
R = 8.314
T = temperature in Kelvin (284.2 K)
M = molar mass in kg/mol (0.0160 kg/mol)

u = square root [3(8.314)(284.2)/0.016) = 666 m/s